Client initiated backups of site data and db?

I'm hoping that there might be a clean way to make the client deal with the backup of their own data (i.e. ispc 2, where the data is placed somewhere that the client can download it and maintain copies)

I have searched, and though there are several "ful server" solutions for imaging and incremental backups, none allow for seperating out by user.

Any help would be great, if nothing else a good learning experience for me.

I've learned more about linux and the server stuff in the last 2 weeks than I thought possible.